Four fire engines and around 25 firefighters were called to a fire at a flat on Portman Square in Marylebone.
A small part of a flat on the ground floor was damaged by the fire. There were no reports of any injuries.
The Brigade was called at 1430 and the fire was under control by 1506. Fire crews from Soho and Paddington fire stations were at the scene.
The Brigade's fire investigators believe the fire was accidental and caused by a halogen down light positioned too close to towels.